Controle estrutural do carste hipogênico Toca da Boa Vista - Toca da Barriguda na formação salitre, norte do Cráton São Francisco

Abstract

Porosity and permeability along fractured zones of carbonate rocks could be enhanced by ascending fluid flow in karst regions. This work presents a structural analysis of two largest hypogenic caves in South America. The study area encompasses the Toca da Boa Vista (TBV) and Toca da Barriguda (TBR) caves, which are 115 km and 32 km long, respectively. This karst system occurs in the Neoproterozoic carbonates of the Salitre Formation, in the northern part of the São Francisco craton. The fold belts around and at the craton edges were deformed during the Brasiliano orogeny in a compressive setting at 740-580 Ma. Methodology includes maps of conduits available by Bambuí Group of Speleological Research, which were used to constructo structural maps of caves and comparison to regional deformation. The following softwares were used to process structural data: Openstereo, Stereonet 8, Georient 9.4.5 e Tectonic FP. Analysis of deformation of TBV-TBR system and the context of Salitre Formation allowed to conclude that: i) Cave passages developed subhorizontally along (a) N-S and (b) ENE to E-W-oriented anticlines hinges; ii) Karst development were formed by dissolution of subvertical joints, iii) The first folding event F1 corresponds to a N-S-trending compression, probably during Brasiliano event whereas the second event F2, is related a E-W-compression, probably more recent than Brasiliano event. So, it is possible to confirm that fluid flow and related dissolution pathways have a close relationship with regional deformation.